Field of the Invention
The invention relates to a sensor device disposed in a wheel, in particular in the wheel of a motor vehicle. It also relates to a method and a device for monitoring the sensor device, and to a system having the sensor device. The monitoring of parameters of a motor vehicle wheel can make a major contribution to the safety of the motor vehicle occupants. Monitoring of the tire pressure, in particular, plays a very important part in this. Falling tire pressure can provide an early warning of damage to the tire of a motor vehicle wheel. This results in that the attention of the driver of the motor vehicle can then be drawn to a damaged tire in good time, before the tire possibly bursts and there is thus considerable risk of an accident.
Published, non-prosecuted German patent application DE 101 35 936 A1 (corresponding to U.S. Patent Application Publication 2003/0020604 A1 and U.S. Pat. No. 6,690,271 B2) discloses a device for monitoring at least one parameter for a plurality of motor vehicle wheels. On each wheel the device has associated detector units, each having a transmitter unit that transmits a phase-modulated or frequency-modulated signal to a central evaluation and control unit. Each detector unit transmits, at specific time intervals, a brief signal containing a unique identifier. After a wheel change, in an assignment mode of the detector unit and of the central evaluation and control unit, the detector unit in question can be reassigned to the relevant wheel positions by registration of a profile of the mean reception power for each detector unit as a function of the angular position of the respective wheel and by comparison of this with stored signature information. Each detector unit contains an acceleration sensor. The measurement signal of the acceleration sensor is used to detect whether there is a wheel revolution.
Published, non-prosecuted German patent Application DE 101 44 326 A1 (corresponding to U.S. Patent Application Publication No. 2003/0079536 A1 and U.S. Pat. No. 6,748,799 B2) discloses a method and a system for monitoring tire air pressure. A pressure sensor for registering the air pressure inside the tire is disposed in the motor vehicle tire. The output signal from the pressure sensor is transmitted to an evaluation unit via a radio transmission link. The air pressure inside the tire is measured and compared with an optimum tire pressure. If the two pressures differ by more than a predetermined deviation, a deviation signal is generated.
For a sensor device to function properly, it is important for the device to be located in its predefined mounting position inside the wheel. The detachment of the sensor device from its mounting position can lead, first, to failure of the sensor device but also, second, to the destruction of the tire.